I find car cleaning a waste of time. Leave it and just put it out on drive when heavy rain forecast, and it never looks to bad.
The garage that do my annual service always wash and clean inside and out after, so I never bother from one year to the next.
I always remove the beer cans, fag ends, used rubbers, and Macdonalds stuff before each service, as I don't want the garage to think I am some sort of slob!